African Fusion June 2015

35 / 48

June 2015 AFRICAN FUSION 33
Centralised systems such as Murray and Roberts’
installation at the Medupi Welder Training Centre
use variable speed drives (VSDs) on the fans. When a
welder begins to weld, the damper in the telescopic
extraction arm automatically opens to allow the
fume to be extracted. On opening, a signal is sent to
the VSD to increase the fan speed and accommodate
the additional flow.
at source solutions
safe and environmentally responsible
way,” he advises.
Small and mobile fume extraction
While Envirox offers solutions for gen-
eral industry – including plasma cutting
extraction systems, oil-mist filtration
on the CNC side, and complete work-
shop systems that can extract dust off
the floor to keep it clean – “our niche
focus in South Africa is welding fume.
We offer everything from small (0.7 to
2.2 kW) mobile systems for occasional
welding, to very large systems extracting
20 000 m3 /h or more,” says Hoon.
Nederman portable fans are simple
and powerful extractor units. They are
compact and easy-to-use with multiple
inlet and outlet connection options. The
smallest is the Fume Eliminator, which
is a small, lightweight, portable unit
designed to be carried to the working
area. These units provide an airflow
of 150 m3/h, use disposable cartridge-
type filters and are ideal for on-torch
extraction. FilterCart is another mobile
extractionand filter unit for lightwelding
applications. These come with an arm
length of 2.0 or 3.0 m and are suitable
for up to 1 050 m3/h over a filter area
of 35 m2 .
Where a mobile solution for con-
tinuous welding and dust extraction is
required – for large fabrications on an
open shop floor, for example – Neder-
man has developed the Filterbox,
which can be used with more that one
extraction arm. “These systems have
a self cleaning filter that operates via
reverse pulse compressed air, along
with a scraper. As with large-scale dust
collectors, the dust is dropped into a
collector below the unit for safe disposal
after use,” Hoon tells African Fusion,
adding that these Nederman systems
are “among the most cost effective
small system available” and the range
can be “customised to suit almost any
workshop application”.
Twelve Nederman mobile filtration
systems have recently been supplied to
Kumba IronOre for itswelding activities,
to overcome the limitation of a 3.0 m
radius arm.
Centralised extraction and
filtration systems
Nederman centralised systems are
available with three dust collection
variations, Filtermax, FMC andMJC, and
are installed with all of the ducting
extraction arms and fans required
for each particular application. “At
the starting point of the design of
a fume extraction system is
Nederman’s NetQuote de-
sign software. Basedonabasic
specification, this ‘app’ can
produce a 3D drawing of
a fume extraction system
within 10 minutes, including all of the
fan, ducting and extraction arm sizes.
The software will also produce system
performance curves that show the re-
lationship between pressure, flow and
power for different operating points,”
Hoon says.
Highlighting Envirox’s capability,
according to Herteberger is
the centralised ex-
traction installation
at Murray and Rob-
ert’s Medupi welder
training centre in Lep-
halale. “This is our
biggest installation
to-date. It consists
of two independent
18.5 kWsystems, with
30 telescopic arms
connected to each
system.
“To cater for the
variation in the num-
ber of welders being
trained at any one time,
Murray andRoberts chose
to use variable speed drives (VSDs) on
the fans of both systems. When awelder
begins to weld, the damper in the tele-
scopic extraction arm automatically
opens to allow the fume to be extracted.
On opening, a signal is sent to the VSD
to increase the fan speed and accom-
modate the additional flow. So the fan
speed adjusts to the total extraction
requirement, speeding up when more
welders are busy and slowing down as
eachwelder stopswelding. This ensures
that the energy use of the systemmatch-
es the extraction demand and that the
fan is never running at an unnecessary
speed,” Herteberger explains.
“These systems are necessary for
welding operations to comply with
health and safety regulations – and
almost every workshop has a welder
on its premises,” says Hoon. “The OHS
Act specifies that youmust create a safe
environment for your employees, while
ISO 14000 specifies the exact allowable
values. All European companies are
now tending to adopt these globally
accepted standards and even our mines
are mindful of the air their workers are
breathing.
“We are proud promoters of at-
source solutions. Not only is this safer,
but it also saves energy, because less
airflow is needed. Nederman’s at-source
solutions range from the most cost ef-
fective portable and mobile solutions
available through to very large, modern
andhighly efficient centraliseddesigns,”
he concludes.
Nederman’s FilterMax DF solution is a
modular, efficient and compact centralised
solution for dust and fume problems with
capacity to handle
up to 13 000 m3/h
from a single unit.